Ok so first imma hit you with some knowledge. Then im going to give the run down.
Knowledge: Some junglers are better at ganking than others and some cant really do it till level 6.
vs
. Lee sin is going to have more pressure pre 6. But post 6 diana is going to have more lethal ganks. Laners need to know this and play safe until their jungler comes online and is able to start doing things.
Rundown: Jungle Runs on an XP and a gold deficit. We get less gold and less xp than laners. This forces us to only go for the ganks that are set up. This means the enemy laner must be damaged to at minimum 3/4 hp. and the be pushed up. Also they cant be too far ahead or its gonna mean we die too because believe it or not we do jack shit for damage before we get items.
If you are 0/2 before we finish our first clear we arent going to help you. You are a lost cause. We are going to let nature take its course instead of suiciding into the lane and giving the laner who is already ahead 2 more additional kills. Now we might gank another lane and then contract their help to 3 man gank the other lane. This happens fairly often. But if you are 0/3 before we can get the other lane there..... well you are on your own buddy.
Now for a quick insight into the mind of the jungler!!!
"I could gank for the 0/3 Darius top and die to the 3/0 fiora with a black cleaver at 10min in...... or i could gank for our 1/0/0 syndra mid and get her further ahead so we can shut down the fiora later in the game"
I think its a pretty easy decision